Method for controlling a powertrain system based upon torque machine temperature

ABSTRACT

A powertrain system includes an engine coupled to an input member of a transmission device operative to transmit torque between the input member and a torque machine and an output member. The torque machine is connected to an energy storage device. A method for controlling the powertrain system include monitoring a temperature of the torque machine, selecting a candidate powertrain system operating point, determining an electrical power input and a motor power output of the torque machine for the candidate powertrain system operating point, determining a power loss for the torque machine associated with the motor power output of the torque machine and the electrical power input, and determining operating costs for operating the powertrain system at the candidate powertrain system operating point associated with the power loss from the torque machine and based upon the temperature of the torque machine.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/985,260 filed on Nov. 4, 2007 which is hereby incorporated herein byreference.

TECHNICAL FIELD

This disclosure is related to power control within a powertrain system.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Known powertrain architectures include torque-generative devices,including internal combustion engines and electric machines, whichtransmit torque through a transmission device to an output member. Oneexemplary powertrain includes a two-mode, compound-split,electro-mechanical transmission which utilizes an input member forreceiving motive torque from a prime mover power source, preferably aninternal combustion engine, and an output member. The output member canbe operatively connected to a driveline for a motor vehicle fortransmitting tractive torque thereto. Electric machines, operative asmotors or generators, generate a torque input to the transmission,independently of a torque input from the internal combustion engine. Theelectric machines may transform vehicle kinetic energy, transmittedthrough the vehicle driveline, to electrical energy that is storable inan electrical energy storage device. A control system monitors variousinputs from the vehicle and the operator and provides operationalcontrol of the powertrain, including controlling transmission operatingstate and gear shifting, controlling the torque-generative devices, andregulating the electrical power interchange among the electrical energystorage device and the electric machines to manage outputs of thetransmission, including torque and rotational speed.

SUMMARY

A powertrain system includes an engine coupled to an input member of atransmission device operative to transmit torque between the inputmember and a torque machine and an output member. The torque machine isconnected to an energy storage device. A method for controlling thepowertrain system include monitoring a temperature of the torquemachine, selecting a candidate powertrain system operating point,determining an electrical power input and a motor power output of thetorque machine for the candidate powertrain system operating point,determining a power loss for the torque machine associated with themotor power output of the torque machine and the electrical power input,and determining operating costs for operating the powertrain system atthe candidate powertrain system operating point associated with thepower loss from the torque machine and based upon the temperature of thetorque machine.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an exemplary hybrid powertrain, inaccordance with the present disclosure;

FIG. 2 is a schematic diagram of an exemplary architecture for a controlsystem and hybrid powertrain, in accordance with the present disclosure;

FIGS. 3-9 are schematic flow diagrams of a control scheme, in accordancewith the present disclosure;

FIG. 10 is a schematic power flow diagram, in accordance with thepresent disclosure; and

FIGS. 11-12 depict a penalty cost determination scheme in accordancewith the present disclosure.

DETAILED DESCRIPTION

Referring now to the drawings, wherein the showings are for the purposeof illustrating certain exemplary embodiments only and not for thepurpose of limiting the same, FIGS. 1 and 2 depict an exemplary hybridpowertrain system. The exemplary hybrid powertrain system in accordancewith the present disclosure is depicted in FIG. 1, comprising atwo-mode, compound-split, electro-mechanical hybrid transmission 10operatively connected to an engine 14 and torque machines comprisingfirst and second electric machines (‘MG-A’) 56 and (‘MG-B’) 72. Theengine 14 and first and second electric machines 56 and 72 each generatemechanical power which can be transferred to the transmission 10. Thepower generated by the engine 14 and the first and second electricmachines 56 and 72 and transferred to the transmission 10 is describedin terms of input and motor torques, referred to herein as T_(I), T_(A),and T_(B) respectively, and speed, referred to herein as N_(I), N_(A),and N_(B), respectively.

The exemplary engine 14 comprises a multi-cylinder internal combustionengine selectively operative in several states to transfer torque to thetransmission 10 via an input shaft 12, and can be either aspark-ignition or a compression-ignition engine. The engine 14 includesa crankshaft (not shown) operatively coupled to the input shaft 12 ofthe transmission 10. A rotational speed sensor 11 monitors rotationalspeed of the input shaft 12. Power output from the engine 14, comprisingrotational speed and engine torque, can differ from the input speedN_(I) and the input torque T_(I) to the transmission 10 due to placementof torque-consuming components on the input shaft 12 between the engine14 and the transmission 10, e.g., a hydraulic pump (not shown) and/or atorque management device (not shown).

The exemplary transmission 10 comprises three planetary-gear sets 24, 26and 28, and four selectively engageable torque-transferring devices,i.e., clutches C1 70, C2 62, C3 73, and C4 75. As used herein, clutchesrefer to any type of friction torque transfer device including single orcompound plate clutches or packs, band clutches, and brakes, forexample. A hydraulic control circuit 42, preferably controlled by atransmission control module (hereafter ‘TCM’) 17, is operative tocontrol clutch states. Clutches C2 62 and C4 75 preferably comprisehydraulically-applied rotating friction clutches. Clutches C1 70 and C373 preferably comprise hydraulically-controlled stationary devices thatcan be selectively grounded to a transmission case 68. Each of theclutches C1 70, C2 62, C3 73, and C4 75 is preferably hydraulicallyapplied, selectively receiving pressurized hydraulic fluid via thehydraulic control circuit 42.

The first and second electric machines 56 and 72 preferably comprisethree-phase AC machines, each including a stator (not shown) and a rotor(not shown), and respective resolvers 80 and 82. The motor stator foreach machine is grounded to an outer portion of the transmission case68, and includes a stator core with coiled electrical windings extendingtherefrom. The rotor for the first electric machine 56 is supported on ahub plate gear that is operatively attached to shaft 60 via the secondplanetary gear set 26. The rotor for the second electric machine 72 isfixedly attached to a sleeve shaft hub 66.

Each of the resolvers 80 and 82 preferably comprises a variablereluctance device including a resolver stator (not shown) and a resolverrotor (not shown). The resolvers 80 and 82 are appropriately positionedand assembled on respective ones of the first and second electricmachines 56 and 72. Stators of respective ones of the resolvers 80 and82 are operatively connected to one of the stators for the first andsecond electric machines 56 and 72. The resolver rotors are operativelyconnected to the rotor for the corresponding first and second electricmachines 56 and 72. Each of the resolvers 80 and 82 is signally andoperatively connected to a transmission power inverter control module(hereafter ‘TPIM’) 19, and each senses and monitors rotational positionof the resolver rotor relative to the resolver stator, thus monitoringrotational position of respective ones of first and second electricmachines 56 and 72. Additionally, the signals output from the resolvers80 and 82 are interpreted to provide the rotational speeds for first andsecond electric machines 56 and 72, i.e., N_(A) and N_(B), respectively.

The transmission 10 includes an output member 64, e.g. a shaft, which isoperably connected to a driveline 90 for a vehicle (not shown), toprovide output power to the driveline 90 that is transferred to vehiclewheels 93, one of which is shown in FIG. 1. The output power at theoutput member 64 is characterized in terms of an output rotational speedN_(O) and an output torque T_(O). A transmission output speed sensor 84monitors rotational speed and rotational direction of the output member64. Each of the vehicle wheels 93 is preferably equipped with a frictionbrake 94 and a sensor (not shown) adapted to monitor wheel speed, theoutput of which is monitored by a control module of a distributedcontrol module system described with respect to FIG. 2, to determinevehicle speed, and absolute and relative wheel speeds for brakingcontrol, traction control, and vehicle acceleration management.

The input torque from the engine 14 and the motor torques from the firstand second electric machines 56 and 72 (T_(I), T_(A), and T_(B)respectively) are generated as a result of energy conversion from fuelor electrical potential stored in an electrical energy storage device(hereafter ‘ESD’) 74. The ESD 74 is high voltage DC-coupled to the TPIM19 via DC transfer conductors 27. The transfer conductors 27 include acontactor switch 38. When the contactor switch 38 is closed, undernormal operation, electric current can flow between the ESD 74 and theTPIM 19. When the contactor switch 38 is opened electric current flowbetween the ESD 74 and the TPIM 19 is interrupted. The TPIM 19 transmitselectrical power to and from the first electric machine 56 by transferconductors 29, and the TPIM 19 similarly transmits electrical power toand from the second electric machine 72 by transfer conductors 31 tomeet the torque commands for the first and second electric machines 56and 72 in response to the motor torque commands T_(A) and T_(B).Electrical current is transmitted to and from the ESD 74 in accordancewith whether the ESD 74 is being charged or discharged.

The TPIM 19 includes the pair of power inverters (not shown) andrespective motor control modules (not shown) configured to receive themotor torque commands and control inverter states therefrom forproviding motor drive or regeneration functionality to meet thecommanded motor torques T_(A) and T_(B). The power inverters compriseknown complementary three-phase power electronics devices, and eachincludes a plurality of insulated gate bipolar transistors (not shown)for converting DC power from the ESD 74 to AC power for poweringrespective ones of the first and second electric machines 56 and 72, byswitching at high frequencies. The insulated gate bipolar transistorsform a switch mode power supply configured to receive control commands.There is typically one pair of insulated gate bipolar transistors foreach phase of each of the three-phase electric machines. States of theinsulated gate bipolar transistors are controlled to provide motor drivemechanical power generation or electric power regenerationfunctionality. The three-phase inverters receive or supply DC electricpower via DC transfer conductors 27 and transform it to or fromthree-phase AC power, which is conducted to or from the first and secondelectric machines 56 and 72 for operation as motors or generators viatransfer conductors 29 and 31 respectively.

FIG. 2 is a schematic block diagram of the distributed control modulesystem. The elements described hereinafter comprise a subset of anoverall vehicle control architecture, and provide coordinated systemcontrol of the exemplary hybrid powertrain described in FIG. 1. Thedistributed control module system synthesizes pertinent information andinputs, and executes algorithms to control various actuators to meetcontrol objectives, including objectives related to fuel economy,emissions, performance, drivability, and protection of hardware,including batteries of ESD 74 and the first and second electric machines56 and 72. The distributed control module system includes an enginecontrol module (hereafter ‘ECM’) 23, the TCM 17, a battery pack controlmodule (hereafter ‘BPCM’) 21, and the TPIM 19. A hybrid control module(hereafter ‘HCP’) 5 provides supervisory control and coordination of theECM 23, the TCM 17, the BPCM 21, and the TPIM 19. A user interface(‘UI’) 13 is operatively connected to a plurality of devices throughwhich a vehicle operator controls or directs operation of theelectro-mechanical hybrid powertrain. The devices include an acceleratorpedal 113 (‘AP’), an operator brake pedal 112 (‘BP’), a transmissiongear selector 114 (‘PRNDL’), and a vehicle speed cruise control (notshown). The transmission gear selector 114 may have a discrete number ofoperator-selectable positions, including the rotational direction of theoutput member 64 to enable one of a forward and a reverse direction.

The aforementioned control modules communicate with other controlmodules, sensors, and actuators via a local area network (hereafter‘LAN’) bus 6. The LAN bus 6 allows for structured communication ofstates of operating parameters and actuator command signals between thevarious control modules. The specific communication protocol utilized isapplication-specific. The LAN bus 6 and appropriate protocols providefor robust messaging and multi-control module interfacing between theaforementioned control modules, and other control modules providingfunctionality including e.g., antilock braking, traction control, andvehicle stability. Multiple communications buses may be used to improvecommunications speed and provide some level of signal redundancy andintegrity. Communication between individual control modules can also beeffected using a direct link, e.g., a serial peripheral interface(‘SPI’) bus (not shown).

The HCP 5 provides supervisory control of the hybrid powertrain, servingto coordinate operation of the ECM 23, TCM 17, TPIM 19, and BPCM 21.Based upon various input signals from the user interface 13 and thehybrid powertrain, including the ESD 74, the HCP 5 determines anoperator torque request, an output torque command, an engine inputtorque command, clutch torque(s) for the applied torque-transferclutches C1 70, C2 62, C3 73, C4 75 of the transmission 10, and themotor torque commands T_(A) and T_(B) for the first and second electricmachines 56 and 72.

The ECM 23 is operatively connected to the engine 14, and functions toacquire data from sensors and control actuators of the engine 14 over aplurality of discrete lines, shown for simplicity as an aggregatebi-directional interface cable 35. The ECM 23 receives the engine inputtorque command from the HCP 5. The ECM 23 determines the actual engineinput torque, T_(I), provided to the transmission 10 at that point intime based upon monitored engine speed and load, which is communicatedto the HCP 5. The ECM 23 monitors input from the rotational speed sensor11 to determine the engine input speed to the input shaft 12, whichtranslates to the transmission input speed, N_(I). The ECM 23 monitorsinputs from sensors (not shown) to determine states of other engineoperating parameters including, e.g., a manifold pressure, enginecoolant temperature, ambient air temperature, and ambient pressure. Theengine load can be determined, for example, from the manifold pressure,or alternatively, from monitoring operator input to the acceleratorpedal 113. The ECM 23 generates and communicates command signals tocontrol engine actuators, including, e.g., fuel injectors, ignitionmodules, and throttle control modules, none of which are shown.

The TCM 17 is operatively connected to the transmission 10 and monitorsinputs from sensors (not shown) to determine states of transmissionoperating parameters. The TCM 17 generates and communicates commandsignals to control the transmission 10, including controlling thehydraulic control circuit 42. Inputs from the TCM 17 to the HCP 5include estimated clutch torques for each of the clutches, i.e., C1 70,C2 62, C3 73, and C4 75, and rotational output speed, N_(O), of theoutput member 64. Other actuators and sensors may be used to provideadditional information from the TCM 17 to the HCP 5 for controlpurposes. The TCM 17 monitors inputs from pressure switches (not shown)and selectively actuates pressure control solenoids (not shown) andshift solenoids (not shown) of the hydraulic control circuit 42 toselectively actuate the various clutches C1 70, C2 62, C3 73, and C4 75to achieve various transmission operating range states, as describedhereinbelow.

The BPCM 21 is signally connected to sensors (not shown) to monitor theESD 74, including states of electrical current and voltage parameters,to provide information indicative of parametric states of the batteriesof the ESD 74 to the HCP 5. The parametric states of the batteriespreferably include battery state-of-charge, battery voltage, batterytemperature, and available battery power, referred to as a range P_(BAT)_(—) _(MIN) to P_(BAT) _(—) _(MAX).

A brake control module (hereafter ‘BrCM’) 22 is operatively connected tothe friction brakes 94 on each of the vehicle wheels 93. The BrCM 22monitors the operator input to the brake pedal 112 and generates controlsignals to control the friction brakes 94 and sends a control signal tothe HCP 5 to operate the first and second electric machines 56 and 72based thereon, to effect vehicle braking through a process referred toas blended braking.

Each of the control modules ECM 23, TCM 17, TPIM 19, BPCM 21, and BrCM22 is preferably a general-purpose digital computer comprising amicroprocessor or central processing unit, storage mediums comprisingread only memory (‘ROM’), random access memory (‘RAM’), electricallyprogrammable read only memory (‘EPROM’), a high speed clock, analog todigital (‘A/D’) and digital to analog (‘D/A’) circuitry, andinput/output circuitry and devices (‘I/O’) and appropriate signalconditioning and buffer circuitry. Each of the control modules has a setof control algorithms, comprising resident program instructions andcalibrations stored in one of the storage mediums and executed toprovide the respective functions of each computer. Information transferbetween the control modules is preferably accomplished using the LAN bus6 and SPI buses. The control algorithms are executed during preset loopcycles such that each algorithm is executed at least once each loopcycle. Algorithms stored in the non-volatile memory devices are executedby one of the central processing units to monitor inputs from thesensing devices and execute control and diagnostic routines to controloperation of the actuators, using preset calibrations. Loop cycles areexecuted at regular intervals, for example each 3.125, 6.25, 12.5, 25and 100 milliseconds during ongoing operation of the hybrid powertrain.Alternatively, algorithms may be executed in response to the occurrenceof an event.

The exemplary hybrid powertrain selectively operates in one of severalstates that can be described in terms of engine states comprising one ofan engine-on state (‘ON’) and an engine-off state (‘OFF’), andtransmission operating range states comprising a plurality of fixedgears and continuously variable operating modes, described withreference to Table 1, below.

TABLE 1 Engine Transmission Operating Applied Description State RangeState Clutches M1_Eng_Off OFF EVT Mode 1 C1 70 M1_Eng_On ON EVT Mode 1C1 70 G1 ON Fixed Gear Ratio 1 C1 70 C4 75 G2 ON Fixed Gear Ratio 2 C170 C2 62 M2_Eng_Off OFF EVT Mode 2 C2 62 M2_Eng_On ON EVT Mode 2 C2 62G3 ON Fixed Gear Ratio 3 C2 62 C4 75 G4 ON Fixed Gear Ratio 4 C2 62 C373

Each of the transmission operating range states is described in thetable and indicates which of the specific clutches C1 70, C2 62, C3 73,and C4 75 are applied for each of the operating range states. A firstcontinuously variable mode, i.e., EVT Mode 1, or M1, is selected byapplying clutch C1 70 only in order to “ground” the outer gear member ofthe third planetary gear set 28. The engine state can be one of ON(‘M1_Eng_On’) or OFF (‘M1_Eng_Off’). A second continuously variablemode, i.e., EVT Mode 2, or M2, is selected by applying clutch C2 62 onlyto connect the shaft 60 to the carrier of the third planetary gear set28. The engine state can be one of ON (‘M2_Eng_On’) or OFF(‘M2_Eng_Off’). For purposes of this description, when the engine stateis OFF, the engine input speed is equal to zero revolutions per minute(‘RPM’), i.e., the engine crankshaft is not rotating. A fixed gearoperation provides a fixed ratio operation of input-to-output speed ofthe transmission 10, i.e., N_(I)/N_(O). A first fixed gear operation(‘G1’) is selected by applying clutches C1 70 and C4 75. A second fixedgear operation (‘G2’) is selected by applying clutches C1 70 and C2 62.A third fixed gear operation (‘G3’) is selected by applying clutches C262 and C4 75. A fourth fixed gear operation (‘G4’) is selected byapplying clutches C2 62 and C3 73. The fixed ratio operation ofinput-to-output speed increases with increased fixed gear operation dueto decreased gear ratios in the planetary gears 24, 26, and 28. Therotational speeds of the first and second electric machines 56 and 72,N_(A) and N_(B) respectively, are dependent on internal rotation of themechanism as defined by the clutching and are proportional to the inputspeed measured at the input shaft 12.

In response to operator input via the accelerator pedal 113 and brakepedal 112 as captured by the user interface 13, the HCP 5 and one ormore of the other control modules determine torque commands to controlthe torque generative devices comprising the engine 14 and the first andsecond electric machines 56 and 72 to meet the operator torque requestat the output member 64 and transferred to the driveline 90. Based uponinput signals from the user interface 13 and the hybrid powertrainincluding the ESD 74, the HCP 5 determines the operator torque request,a commanded output torque from the transmission 10 to the driveline 90,an input torque from the engine 14, clutch torques for thetorque-transfer clutches C1 70, C2 62, C3 73, C4 75 of the transmission10; and the motor torques for the first and second electric machines 56and 72, respectively, as is described hereinbelow.

Final vehicle acceleration can be affected by other factors including,e.g., road load, road grade, and vehicle mass. The engine state and thetransmission operating range state are determined based upon a varietyof operating characteristics of the hybrid powertrain. This includes theoperator torque request communicated through the accelerator pedal 113and brake pedal 112 to the user interface 13 as previously described.The transmission operating range state and the engine state may bepredicated on a hybrid powertrain torque demand caused by a command tooperate the first and second electric machines 56 and 72 in anelectrical energy generating mode or in a torque generating mode. Thetransmission operating range state and the engine state can bedetermined by an optimization algorithm or routine which determinesoptimum system efficiency based upon operator demand for power, batterystate of charge, and energy efficiencies of the engine 14 and the firstand second electric machines 56 and 72. The control system managestorque inputs from the engine 14 and the first and second electricmachines 56 and 72 based upon an outcome of the executed optimizationroutine, and system efficiencies are optimized thereby, to manage fueleconomy and battery charging. Furthermore, operation can be determinedbased upon a fault in a component or system. The HCP 5 monitors thetorque-generative devices, and determines the power output from thetransmission 10 at output member 64 that is required to meet theoperator torque request while meeting other powertrain operatingdemands, e.g., charging the ESD 74. As should be apparent from thedescription above, the ESD 74 and the first and second electric machines56 and 72 are electrically-operatively coupled for power flowtherebetween. Furthermore, the engine 14, the first and second electricmachines 56 and 72, and the electro-mechanical transmission 10 aremechanically-operatively coupled to transfer power therebetween togenerate a power flow to the output member 64.

FIG. 3 shows a control system architecture for controlling and managingsignal flow in a hybrid powertrain system having multiple torquegenerative devices, described hereinbelow with reference to the hybridpowertrain system of FIGS. 1 and 2, and residing in the aforementionedcontrol modules in the form of executable algorithms and calibrations.The control system architecture is applicable to alternative hybridpowertrain systems having multiple torque generative devices, including,e.g., a hybrid powertrain system having an engine and a single electricmachine, a hybrid powertrain system having an engine and multipleelectric machines. Alternatively, the hybrid powertrain system canutilize non-electric torque-generative machines and energy storagesystems, e.g., hydraulic-mechanical hybrid transmissions (not shown).

In operation, the operator inputs to the accelerator pedal 113 and thebrake pedal 112 are monitored to determine the operator torque request.The operator inputs to the accelerator pedal 113 and the brake pedal 112comprise individually determinable operator torque request inputsincluding an immediate accelerator output torque request (‘Output TorqueRequest Accel Immed’), a predicted accelerator output torque request(‘Output Torque Request Accel Prdtd’), an immediate brake output torquerequest (‘Output Torque Request Brake Immed’), a predicted brake outputtorque request (‘Output Torque Request Brake Prdtd’) and an axle torqueresponse type (‘Axle Torque Response Type’). As used herein, the term‘accelerator’ refers to an operator request for forward propulsionpreferably resulting in increasing vehicle speed over the presentvehicle speed, when the operator selected position of the transmissiongear selector 114 commands operation of the vehicle in the forwarddirection. The terms ‘deceleration’ and ‘brake’ refer to an operatorrequest preferably resulting in decreasing vehicle speed from thepresent vehicle speed. The immediate accelerator output torque request,the predicted accelerator output torque request, the immediate brakeoutput torque request, the predicted brake output torque request, andthe axle torque response type are individual inputs to the controlsystem. Additionally, operation of the engine 14 and the transmission 10are monitored to determine the input speed (‘Ni’) and the output speed(‘No’).

The immediate accelerator output torque request comprises an immediatetorque request determined based upon the operator input to theaccelerator pedal 113. The control system controls the output torquefrom the hybrid powertrain system in response to the immediateaccelerator output torque request to cause positive acceleration of thevehicle. The immediate brake output torque request comprises animmediate braking request determined based upon the operator input tothe brake pedal 112. The control system controls the output torque fromthe hybrid powertrain system in response to the immediate brake outputtorque request to cause deceleration, or negative acceleration, of thevehicle. Vehicle deceleration effected by control of the output torquefrom the hybrid powertrain system is combined with vehicle decelerationeffected by a vehicle braking system (not shown) to decelerate thevehicle to achieve the immediate braking request.

The immediate accelerator output torque request is determined based upona presently occurring operator input to the accelerator pedal 113, andcomprises a request to generate an immediate output torque at the outputmember 64 preferably to accelerate the vehicle. The immediateaccelerator output torque request is unshaped, but can be shaped byevents that affect vehicle operation outside the powertrain control.Such events include vehicle level interruptions in the powertraincontrol for antilock braking, traction control and vehicle stabilitycontrol, which can be used to unshape or rate-limit the immediateaccelerator output torque request.

The predicted accelerator output torque request is determined based uponthe operator input to the accelerator pedal 113 and comprises an optimumor preferred output torque at the output member 64. The predictedaccelerator output torque request is preferably equal to the immediateaccelerator output torque request during normal operating conditions,e.g., when any one of antilock braking, traction control, or vehiclestability is not being commanded. When any one of antilock braking,traction control or vehicle stability is being commanded the predictedaccelerator output torque request remains the preferred output torquewith the immediate accelerator output torque request being decreased inresponse to output torque commands related to the antilock braking,traction control, or vehicle stability control.

The immediate brake output torque request is determined based upon theoperator input to the brake pedal 112 and the control signal to controlthe friction brakes 94 to generate friction braking torque.

The predicted brake output torque request comprises an optimum orpreferred brake output torque at the output member 64 in response to anoperator input to the brake pedal 112 subject to a maximum brake outputtorque generated at the output member 64 allowable regardless of theoperator input to the brake pedal 112. In one embodiment the maximumbrake output torque generated at the output member 64 is limited to −0.2g. The predicted brake output torque request can be phased out to zerowhen vehicle speed approaches zero regardless of the operator input tothe brake pedal 112. As desired by a user, there can be operatingconditions under which the predicted brake output torque request is setto zero, e.g., when the operator setting to the transmission gearselector 114 is set to a reverse gear, and when a transfer case (notshown) is set to a four-wheel drive low range. The operating conditionswhereat the predicted brake output torque request is set to zero arethose in which blended braking is not preferred due to vehicle operatingfactors.

The axle torque response type comprises an input state for shaping andrate-limiting the output torque response through the first and secondelectric machines 56 and 72. The input state for the axle torqueresponse type can be an active state, preferably comprising one of apleasability limited state a maximum range state, and an inactive state.When the commanded axle torque response type is the active state, theoutput torque command is the immediate output torque. Preferably thetorque response for this response type is as fast as possible.

Blended braking includes generating friction braking torque at thewheels 93 and generating output torque at the output member 64 to reactwith the driveline 90 to decelerate the vehicle in response to theoperator input to the brake pedal 112. The BrCM 22 commands the frictionbrakes 94 to apply braking torque and generates a command for thetransmission 10 to create a negative output torque which reacts with thedriveline 90 in response to the immediate braking request. Preferablythe applied braking torque and the negative output torque can decelerateand stop the vehicle so long as they are sufficient to overcome vehiclekinetic power at wheel(s) 93. The negative output torque reacts with thedriveline 90, thus transferring torque to the electro-mechanicaltransmission 10 and the engine 14. The negative output torque reactedthrough the electro-mechanical transmission 10 can be transferred to oneor both of the first and second electric machines 56 and 72 to generateelectric power for storage in the ESD 74.

A strategic optimization control scheme (‘Strategic Control’) 310determines a preferred input speed (‘Ni_Des’) and a preferred enginestate and transmission operating range state (‘Hybrid Range State Des’)based upon the output speed and the operator torque request and basedupon other operating parameters of the hybrid powertrain, includingbattery power limits and response limits of the engine 14, thetransmission 10, and the first and second electric machines 56 and 72.The predicted accelerator output torque request and the predicted brakeoutput torque request are input to the strategic optimization controlscheme 310. The strategic optimization control scheme 310 is preferablyexecuted by the HCP 5 during each 100 ms loop cycle and each 25 ms loopcycle. The desired operating range state for the transmission 10 and thedesired input speed from the engine 14 to the transmission 10 are inputsto the shift execution and engine start/stop control scheme 320.

The shift execution and engine start/stop control scheme 320 commandschanges in the transmission operation (‘Transmission Commands’)including changing the operating range state based upon the inputs andoperation of the powertrain system. This includes commanding executionof a change in the transmission operating range state if the preferredoperating range state is different from the present operating rangestate by commanding changes in application of one or more of theclutches C1 70, C2 62, C3 73, and C4 75 and other transmission commands.The present operating range state (‘Hybrid Range State Actual’) and aninput speed profile (‘Ni_Prof’) can be determined. The input speedprofile is an estimate of an upcoming input speed and preferablycomprises a scalar parametric value that is a targeted input speed forthe forthcoming loop cycle. The engine operating commands and theoperator torque request are based upon the input speed profile during atransition in the operating range state of the transmission.

A tactical control scheme (‘Tactical Control and Operation’) 330 isrepeatedly executed during one of the control loop cycles to determineengine commands (‘Engine Commands’) for operating the engine 14,including a preferred input torque from the engine 14 to thetransmission 10 based upon the output speed, the input speed, and theoperator torque request comprising the immediate accelerator outputtorque request, the predicted accelerator output torque request, theimmediate brake output torque request, the predicted brake output torquerequest, the axle torque response type, and the present operating rangestate for the transmission. The engine commands also include enginestates including one of an all-cylinder operating state and a cylinderdeactivation operating state wherein a portion of the engine cylindersare deactivated and unfueled, and engine states including one of afueled state and a fuel cutoff state. An engine command comprising thepreferred input torque of the engine 14 and a present input torque(‘Ti’) reacting between the engine 14 and the input member 12 arepreferably determined in the ECM 23. Clutch torques (‘Tcl’) for each ofthe clutches C1 70, C2 62, C3 73, and C4 75, including the presentlyapplied clutches and the non-applied clutches are estimated, preferablyin the TCM 17.

An output and motor torque determination scheme (‘Output and MotorTorque Determination’) 340 is executed to determine the preferred outputtorque from the powertrain (‘To_cmd’). This includes determining motortorque commands (‘T_(A)’, ‘T_(B)’) to transfer a net commanded outputtorque to the output member 64 of the transmission 10 that meets theoperator torque request, by controlling the first and second electricmachines 56 and 72 in this embodiment. The immediate accelerator outputtorque request, the immediate brake output torque request, the presentinput torque from the engine 14 and the estimated applied clutchtorque(s), the present operating range state of the transmission 10, theinput speed, the input speed profile, and the axle torque response typeare inputs. The output and motor torque determination scheme 340executes to determine the motor torque commands during each iteration ofone of the loop cycles. The output and motor torque determination scheme340 includes algorithmic code which is regularly executed during the6.25 ms and 12.5 ms loop cycles to determine the preferred motor torquecommands.

The hybrid powertrain is controlled to transfer the output torque to theoutput member 64 to react with the driveline 90 to generate tractivetorque at wheel(s) 93 to forwardly propel the vehicle in response to theoperator input to the accelerator pedal 113 when the operator selectedposition of the transmission gear selector 114 commands operation of thevehicle in the forward direction. Similarly, the hybrid powertrain iscontrolled to transfer the output torque to the output member 64 toreact with the driveline 90 to generate tractive torque at wheel(s) 93to propel the vehicle in a reverse direction in response to the operatorinput to the accelerator pedal 113 when the operator selected positionof the transmission gear selector 114 commands operation of the vehiclein the reverse direction. Preferably, propelling the vehicle results invehicle acceleration so long as the output torque is sufficient toovercome external loads on the vehicle, e.g., due to road grade,aerodynamic loads, and other loads.

FIG. 4 details signal flow in the tactical control scheme (‘TacticalControl and Operation’) 330 for controlling operation of the engine 14,described with reference to the hybrid powertrain system of FIGS. 1 and2 and the control system architecture of FIGS. 3 and 4. The tacticalcontrol scheme 330 includes a tactical optimization control path 350 anda system constraints control path 360 which are preferably executedconcurrently. The outputs of the tactical optimization control path 350are input to an engine state control scheme 370. The outputs of theengine state control scheme 370 and the system constraints control path360 are input to an engine response type determination scheme (‘EngineResponse Type Determination’) 380 for controlling the engine state, theimmediate engine torque request, the predicted engine torque request,and the engine response type.

The input from the engine 14 can be described in terms of an engineoperating point including engine speed and engine torque which can beconverted into the input speed and input torque which react with theinput member from the transmission 10. When the engine 14 comprises aspark-ignition engine, a change in the engine operating point can beeffected by changing mass of intake air to the engine 14, by controllingposition of an engine throttle (not shown) utilizing an electronicthrottle control system (not shown), including opening the enginethrottle to increase engine torque and closing the engine throttle todecrease engine torque. Changes in the engine operating point can beeffected by adjusting ignition timing, including retarding spark timingfrom a mean-best-torque spark timing to decrease engine torque. When theengine 14 comprises a compression-ignition engine, the engine operatingpoint is controlled by controlling the mass of injected fuel andadjusted by retarding injection timing from a mean-best-torque injectiontiming to decrease the engine torque. The engine operating point canalso be changed to effect a change in the input torque by controllingthe engine state between the all-cylinder state and the cylinderdeactivation state, and, by controlling the engine state between theengine-fueled state and the fuel cutoff state wherein the engine isrotating and unfueled.

The tactical optimization control path 350 acts on substantiallysteady-state inputs to select a preferred engine state and to determinea preferred input torque from the engine 14 to the transmission 10. Thetactical optimization control path 350 includes an optimization scheme(‘Tactical Optimization’) 354 to determine preferred input torques foroperating the engine 14 in the all-cylinder state (‘Input Torque Full’),in the cylinder deactivation state (‘Input Torque Deac’), theall-cylinder state with fuel cutoff (‘Input Torque Full FCO’), in thecylinder deactivation state with fuel cutoff (‘Input Torque Deac FCO’),and a preferred engine state (‘Preferred Engine State’). Inputs to theoptimization scheme 354 include a lead operating range state of thetransmission 10 (‘Lead Hybrid Range State’) a lead predicted inputacceleration profile (‘Lead Input Acceleration Profile Predicted’) and apredicted range of clutch reactive torques (‘Predicted Clutch ReactiveTorque Min/Max’) across each applied clutch in the lead operating rangestate, which are preferably generated in the shift execution and enginestart/stop control scheme 320. Further inputs include predicted electricpower limits (‘Predicted Battery Power Limits’), a predicted acceleratoroutput torque request (‘Output Torque Request Accel Prdtd’) and apredicted brake output torque request (‘Output Torque Request BrakePrdtd’). The predicted output torque request for acceleration is shapedthrough a predicted output torque shaping filter 352 while consideringthe axle torque response type to yield a predicted accelerator outputtorque (‘To Accel Prdtd’) and combined with the predicted output torquerequest for braking to determine the net predicted output torque (‘ToNet Prdtd’), which are inputs to the optimization scheme 354. The leadoperating range state of the transmission 10 comprises a time-shiftedlead of the operating range state of the transmission 10 to accommodatea response time lag between a commanded change in the operating rangestate and the actual operating range state. Thus the lead operatingrange state of the transmission 10 is the commanded operating rangestate. The lead predicted input acceleration profile comprises atime-shifted lead of the predicted input acceleration profile of theinput member 12 to accommodate a response time lag between a commandedchange in the predicted input acceleration profile and a measured changein the predicted input acceleration profile. Thus the lead predictedinput acceleration profile is the predicted input acceleration profileof the input member 12 occurring after the time shift. The parametersdesignated as ‘lead’ are used to accommodate concurrent transfer oftorque through the powertrain converging at the common output member 64using devices having varying response times. Specifically, the engine 14can have a response time of an order of magnitude of 300-600 ms, andeach of the torque transfer clutches C1 70, C2 62, C3 73, and C4 75 canhave response times of an order of magnitude of 150-300 ms, and thefirst and second electric machines 56 and 72 can have response time ofan order of magnitude of 10 ms.

The optimization scheme 354 determines costs for operating the engine 14in the engine states, which comprise operating the engine fueled and inthe all-cylinder state (‘P_(COST FULL FUEL)’), operating the engineunfueled and in the all-cylinder state (‘P_(COST FULL FCO)’), operatingthe engine fueled and in cylinder deactivation state(‘P_(COST DEAC FUEL)’), and operating the engine unfueled and in thecylinder deactivation state (‘P_(COST DEAC FCO)’). The aforementionedcosts for operating the engine 14 are input to a stabilization analysisscheme (‘Stabilization and Arbitration’) 356 along with the actualengine state (‘Actual Engine State’) and allowable or permissible enginestate(s) (‘Engine State Allowed’) to select one of the engine states asthe preferred engine state (‘Preferred Engine State’).

The preferred input torques for operating the engine 14 in theall-cylinder state and in the cylinder deactivation state with andwithout fuel cutoff are input to an engine torque conversion calculator355 and converted to preferred engine torques in the all-cylinder stateand in the cylinder deactivation state (‘Engine Torque Full’ and ‘EngineTorque Deac’) and with fuel cutoff in the all-cylinder state and in thecylinder deactivation state (‘Engine Torque Full FCO’ and ‘Engine TorqueDeac FCO’) respectively, by taking into account torque-consumingcomponents, e.g., a hydraulic pump, between the engine 14 and thetransmission 10. The preferred engine torques and the preferred enginestate comprise inputs to the engine state control scheme 370.

The costs for operating the engine 14 include operating costs which aredetermined based upon factors that include vehicle driveability, fueleconomy, emissions, and battery usage. Costs are assigned and associatedwith fuel and electrical power consumption and are associated withspecific operating conditions of the hybrid powertrain. Lower operatingcosts can be associated with lower fuel consumption at high conversionefficiencies, lower battery power usage and lower emissions and takeinto account the present operating state of the engine 14.

The preferred engine state and the preferred engine torques in theall-cylinder state and in the cylinder deactivation state are input tothe engine state control scheme 370, which includes an engine statemachine (‘Engine State Machine’) 372. The engine state machine 372determines a target engine torque (‘Target Engine Torque’) and an enginestate (‘Target Engine State’) based upon the preferred engine torquesand the preferred engine state. The target engine torque and the enginestate are input to a transition filter 374 which filters the targetengine torque to provide a filtered target engine torque (‘FilteredTarget Engine Torque’) and which enables transitions between enginestates. The engine state machine 372 outputs a command that indicatesselection of one of the cylinder deactivation state and the all-cylinderstate (‘DEAC Selected’) and indicates selection of one of theengine-fueled state and the deceleration fuel cutoff state (‘FCOSelected’).

The selection of one of the cylinder deactivation state and theall-cylinder state and the selection of one of the engine-fueled stateand the deceleration fuel cutoff state, the filtered target enginetorque, and the minimum and maximum engine torques are input to theengine response type determination scheme 380.

The system constraints control path 360 determines the constraints onthe input torque, comprising minimum and maximum input torques (‘InputTorque Hybrid Minimum’ and ‘Input Torque Hybrid Maximum’) that can bereacted by the transmission 10. The minimum and maximum input torquesare determined based upon constraints to the transmission 10, the firstand second electric machines 56 and 72, and the ESD 74, which affect thecapacity of the transmission 10 and the electric machines 56 and 72.

Inputs to the system constraints control path 360 include the immediateoutput torque request as measured by the accelerator pedal 113 combinedwith the torque intervention control (‘Output Torque Request AccelImmed’) and the immediate output torque request as measured by the brakepedal 112 combined with the torque intervention control (‘Output TorqueRequest Brake Immed’). The immediate output torque request is shapedthrough an immediate output torque shaping filter 362 while consideringthe axle torque response type to yield an immediate accelerator outputtorque (‘To Accel Immed’) and is combined with the immediate outputtorque request for braking to determine the net immediate output torque(‘To Net Immed’). The net immediate output torque and the immediateaccelerator output torque are inputs to a constraints scheme (‘Outputand Input Torque Constraints’) 364. Other inputs to the constraintsscheme 364 include the lead operating range state of the transmission10, an immediate lead input acceleration profile (‘Lead InputAcceleration Profile Immed’), a lead immediate clutch reactive torquerange (‘Lead Immediate Clutch Reactive Torque Min/Max’) for each appliedclutch in the lead operating range state, and the tactical controlelectric power constraints (‘Tactical Control Electric PowerConstraints’) comprising the range from the minimum tactical controlelectric power constraint P_(BAT) _(—) _(MIN) _(—) _(TC) to the maximumtactical control electric power constraint P_(BAT) _(—) _(MAX) _(—)_(TC). The tactical control electric power constraints are outputtedfrom a battery power function (‘Battery Power Control’) 366. A targetedlead input acceleration profile comprises a time-shifted lead of theimmediate input acceleration profile of the input member 12 toaccommodate a response time lag between a commanded change in theimmediate input acceleration profile and a measured change in theimmediate input acceleration profile. The lead immediate clutch reactivetorque range comprises a time-shifted lead of the immediate clutchreactive torque range of the clutches to accommodate a response time lagbetween a commanded change in the immediate clutch torque range and ameasured change in the immediate clutch reactive torque range. Theconstraints scheme 364 determines an output torque range for thetransmission 10, and then determines the minimum and maximum inputtorques that can be reacted by the transmission 10 based upon theaforementioned inputs.

Further, the constraints scheme 364 inputs an immediate engine torquerequest and outputs an immediate electric power P_(BATT) _(—) _(IMMED)that is an estimated battery output power of the ESD 74 when the engine14 is operating at the immediate engine torque and when the electricmachines 56, 72 are operating at preferred motor torques based upon theoperator torque request and the other inputs of the constraints scheme364.

The minimum and maximum input torques are input to the engine torqueconversion calculator 355 and converted to minimum and maximum enginetorques (‘Engine Torque Hybrid Minimum’ and ‘Engine Torque HybridMaximum’ respectively), by taking into account torque-consumingcomponents, e.g., a hydraulic pump, parasitic and other loads introducedbetween the engine 14 and the transmission 10.

The filtered target engine torque, the output of the engine statemachine 372 and the minimum and maximum engine torques are input to theengine response type determination scheme 380. The engine response typedetermination scheme 380 limits the filtered target engine torque to theminimum and maximum hybrid engine torques and outputs the enginecommands to the ECM 23 for controlling the engine torques to animmediate engine torque request (‘Engine Torque Request Immed’) and apredicted engine torque request (‘Engine Torque Request Prdtd’). Othercommands control the engine state to one of the engine fueled state andthe fuel cutoff state (‘FCO Request’) and to one of the cylinderdeactivation state and the all-cylinder state (‘DEAC Request’). Anotheroutput comprises an engine response type (‘Engine Response Type’). Whenthe filtered target engine torque is within the range between theminimum and maximum engine torques, the engine response type isinactive. When the filtered target engine torque drops below the maximumconstraint of the engine torque (‘Engine Torque Hybrid Maximum’) theengine response type is active, indicating a need for an immediatechange in the engine torque, e.g., through engine spark control tochange the engine torque to fall within the constraints of the minimumand maximum engine torques.

FIG. 5 shows details of the tactical optimization scheme 354 of thetactical optimization control path 350. The tactical optimization scheme(‘Tactical Optimization’) 354 is executed to determine preferred inputtorques and associated power costs for operating the engine 14 in theall-cylinder state (‘Input Torque Full’), in the cylinder deactivationstate (‘Input Torque Deac’), the all-cylinder state with fuel cutoff(‘Input Torque Full FCO’), and in the cylinder deactivation state withfuel cutoff (‘Input Torque Deac FCO’). The system inputs to the tacticaloptimization scheme 354, as shown in FIG. 4, include the net predictedoutput torque (‘To Net Prdtd’) and the predicted accelerator outputtorque (‘To Accel Prdtd’). In operation, the predicted acceleratoroutput torque request (‘Output Torque Request Accel Prdtd’) and thepredicted braking output torque request (‘Output Torque Request BrakePrdtd’) are monitored. The predicted output torque requests foracceleration and braking are combined and shaped with the axle torqueresponse type through a predicted output torque shaping filter 352. Thenet predicted output torque comprises a sum of the operator torquerequests communicated through the accelerator pedal 113 and the brakepedal 112. Other inputs include a lead operating range state of thetransmission 10 (‘Lead Hybrid Range State’) a lead predicted inputacceleration profile (‘Lead Input Acceleration Profile Predicted’), apredicted range of clutch reactive torques (‘Predicted Clutch ReactiveTorque Min/Max’) across each applied clutch in the lead operating rangestate, and predicted battery power limits (‘Predicted Battery PowerLimits’).

The lead operating range state of the transmission 10 comprises atime-shifted lead of the operating range state of the transmission 10 toaccommodate a response time lag, for example, between the engine torquerequest and the actual engine torque response. Thus the lead operatingrange state of the transmission 10 becomes the commanded operating rangestate. The lead predicted input acceleration profile comprises atime-shifted lead of the desired predicted input acceleration profile ofthe input member 12 to accommodate the response time lag. Thus the leadpredicted input acceleration profile is the predicted input accelerationprofile of the input member 12 occurring after the time shift. Theparameters designated as ‘lead’ are used to accommodate concurrenttransfer of torque through the powertrain converging at the commonoutput member 64 using devices having varying response times.Specifically, the engine 14 can have a response time of an order ofmagnitude of 300-600 ms, and each of the torque transfer clutches C1 70,C2 62, C3 73, and C4 75 can have response times of an order of magnitudeof 150-300 ms, and the first and second electric machines 56 and 72 canhave response time of an order of magnitude of 10 ms.

The tactical optimization scheme 354 includes an optimization manager420 which manages and generates power cost inputs, penalty costs, andoptimization inputs for search schemes 402 and 406 and evaluationschemes 404 and 408. The search schemes 402 and 406 and evaluationschemes 404 and 408 determine preferred input torques and correspondingoutput torques at minimum power costs for operating the powertrain ateach of the engine states.

The search scheme 402 executes a one-dimensional search of the inputtorque to determine a preferred input torque which minimizes power costswhen operating the engine fueled and in the all-cylinder state. At eachinput torque, a preferred output torque is determined. This includesdetermining a range of input torques comprising minimum and maximuminput torques with the engine 14 operating in the fueled state and inthe all-cylinder state (‘Input Torque Minimum Full’, ‘Input TorqueMaximum Full’) which are input to a one-dimensional search engine 430.The search engine 430 generates a candidate input torque (‘Ti(j)’)within the range of input torques that is input to an optimizationfunction 440. The optimization function 440 calculates outputs includingan output torque (‘To(j)’) and torque outputs from the first and secondelectric machines 56 and 72 (‘Ta(j)’, ‘Tb(j)’), and output power fromthe ESD 74 (‘P_(BAT)(j)’), electrical power from the first and secondelectric machines 56 and 72 (‘Pa(j)’, ‘Pb(j)’) and clutch torque outputs(‘Tcl1(j)’), (‘Tcl2(j)’) of applied clutches of the transmission device10 based upon the candidate input torque and the optimization inputs andthe system inputs. The outputs of the optimization function 440 areinput to a cost function 450 which calculates a power cost(‘P_(COST)(j)’) for the candidate input torque. The search engineiteratively generates candidate input torques and executes over therange of input torques to identify a preferred input torque andcorresponding output torque which achieves a minimum power cost(‘P_(COST FULL FUEL)’) when operating the engine fueled and in theall-cylinder state.

The search scheme 406 executes a one-dimensional search of the inputtorque to determine a preferred input torque which minimizes power costswhen operating the engine fueled and in the cylinder deactivation state.This includes determining a range of input torques comprising minimumand maximum input torques with the engine 14 operating in the fueledstate and in the cylinder deactivation state (‘Input Torque MinimumDeac’, ‘Input Torque Maximum Deac’) which are input to theone-dimensional search engine 430. The search engine 430 generates acandidate input torque (‘Ti(j)’) within the range of input torques thatis input to the optimization function 440. The optimization function 440calculates outputs including an output torque (‘To(j)’) and torqueoutputs from the first and second electric machines 56 and 72 (‘Ta(j)’,‘Tb(j)’), and output power from the ESD 74 (‘P_(BAT)(j)’) and electricalpower from the first and second electric machines 56 and 72 (‘Pa(j)’,‘Pb(j)’) based upon the candidate input torque and the optimizationinputs and the system input. The outputs of the optimization function440 are input to the cost function 450 which calculates a power cost(‘P_(COST)(j)’) for the candidate input torque (‘Ti(j)’). The searchengine iteratively generates candidate input torques and executes overthe range of input torques to identify a preferred input torque andcorresponding output torque which achieves a minimum power cost(‘P_(COST DEAC FUEL)’) when operating the engine in the fueled state andin the cylinder deactivation state.

The evaluation scheme 404 evaluates the input torque to determine apreferred output torque and a power cost when operating the engine inthe unfueled state and in the all-cylinder state. The candidate inputtorque (‘Input Torque FCO Full’) is input to the optimization function440. The optimization function 440 calculates the outputs including anoutput torque (‘To’) and torque outputs from the first and secondelectric machines 56 and 72 (‘Ta’, ‘Tb’), and output power from the ESD74 (‘P_(BAT)’) and power from the first and second electric machines 56and 72 (‘Pa’, ‘Pb’) based upon the input torque and the optimizationinputs and the system inputs. The outputs of the optimization function440 are input to the cost function 450 which calculates a power cost(‘P_(COST FULL FCO)’) when operating the engine unfueled and in theall-cylinder state.

The evaluation scheme 408 evaluates the input torque to determine apreferred output torque and a power cost when operating the engine inthe unfueled state and in the cylinder deactivation state. The candidateinput torque (‘Input Torque FCO Deac’) is input to the optimizationfunction 440. The optimization function 440 calculates the outputsincluding an output torque (‘To’) and torque outputs from the first andsecond electric machines 56 and 72 (‘Ta’, ‘Tb’), and output power fromthe ESD 74 (‘P_(BAT)’) and power from the first and second electricmachines 56 and 72 (‘Pa’, ‘Pb’) based upon the input torque and theoptimization inputs and the system inputs. The outputs of theoptimization function 440 are input to the cost function 450 whichcalculates a power cost (‘P_(COST DEAC FCO)’) for the input torque whenoperating the engine unfueled and in the cylinder deactivation state.

The optimization function 440 has inputs including a single inputtorque, the optimization inputs and the system inputs. The system inputsinclude the net predicted output torque (‘To Net Prdtd’) and thepredicted accelerator output torque (‘To Accel Prdtd’). The optimizationinputs include the lead operating range state of the transmission 10(‘Lead Hybrid Range State’) the lead predicted input accelerationprofile (‘Lead Input Acceleration Profile Predicted’), the predictedrange of clutch reactive torques (‘Predicted Clutch Reactive TorqueMin/Max’) across each applied clutch in the lead operating range state,and predicted battery power limits (‘Predicted Battery Power Limits’).Other limits include maximum and minimum motor torque outputs from thefirst and second electric machines 56 and 72, and system inertias,damping, clutch slippages, and electric/mechanical power conversionefficiencies. For each candidate input torque, the optimization function440 calculates powertrain system outputs that are responsive to thesystem inputs comprising the aforementioned output torque commands andare within the maximum and minimum motor torque outputs from the firstand second electric machines 56 and 72, and within the available batterypower, and within the range of clutch reactive torques from the appliedclutches for the present operating range state of the transmission 10,and take into account the system inertias, damping, clutch slippages,and electric/mechanical power conversion efficiencies. The powertrainsystem outputs include a maximum achievable output torque (‘To’) andachievable torque outputs from the first and second electric machines 56and 72 (‘Ta’, ‘Tb’).

The cost function 450 determines power costs for operating thepowertrain system responsive to the system inputs including the netpredicted output torque and the predicted accelerator output torque andwith the engine 14 at the candidate input torque. The power costs aredetermined based upon factors that include mechanical power loss in theform of friction and spin losses, electrical power losses related toheat generation, internal resistances, and current flow, and parasiticlosses. During braking event, the power costs include kinetic power lossdue to unrecovered kinetic energy that is expended in the form of heatgeneration in the friction brakes 94, which can be recovered as electricpower through regenerative braking. Costs are assigned and associatedwith fuel and electrical power consumption and are associated with aspecific operating point of the hybrid powertrain. Lower power costs areassociated with lower fuel consumption at high conversion efficiencies,lower battery power usage, and lower emissions for each enginespeed/load operating point, and take into account the present operatingstate of the engine 14. The search schemes 402 and 406 includeadditional power costs comprising engine power costs associated withoperating the engine 14 in the all-cylinder fueled state (‘Full CylinderEngine Power Loss Inputs’) and in the cylinder deactivation fueled state(‘Deac Cylinder Engine Power Loss Inputs’).

FIG. 6 details signal flow in the strategic optimization control scheme310, which includes a strategic manager (‘Strategic Manager’) 220, anoperating range state analyzer 260, and a state stabilization andarbitration block 280 to determine the preferred input speed (‘Ni_Des’)and the preferred transmission operating range state (‘Hybrid RangeState Des’). The strategic manager (‘Strategic Manager’) 220 monitorsthe output speed N_(O), the predicted accelerator output torque request(‘Output Torque Request Accel Prdtd’), the predicted brake output torquerequest (‘Output Torque Request Brake Prdtd’), and available batterypower P_(BAT) _(—) _(MIN) to P_(BAT) _(—) _(MAX). The strategic manager220 determines which of the transmission operating range states areallowable, and determines output torque requests comprising a strategicaccelerator output torque request (‘Output Torque Request AccelStrategic’) and a strategic net output torque request (‘Output TorqueRequest Net Strategic’), all of which are input the operating rangestate analyzer 260 along with penalty costs (‘Penalty Costs’), systeminputs (‘System Inputs’) and power cost inputs (‘Power Cost Inputs’).The operating range state analyzer 260 generates a preferred power cost(‘P*cost’) and associated input speed (‘N*i’) for each of the allowableoperating range states based upon the operator torque requests, thesystem inputs, the available battery power and the power cost inputs.The preferred power costs and associated input speeds for the allowableoperating range states are input to the state stabilization andarbitration block 280 which selects the preferred operating range stateand preferred input speed based thereon.

FIG. 7 show the operating range state analyzer 260 which executessearches in each candidate operating range state comprising theallowable ones of the operating range states, including M1 (262), M2(264), G1 (270), G2 (272), G3 (274), and G4 (276) to determine preferredoperation of the torque actuators, i.e., the engine 14 and the first andsecond electric machines 56 and 72 in this embodiment. The preferredoperation preferably comprises a minimum power cost for operating thehybrid powertrain system and an associated engine input for operating inthe candidate operating range state in response to the operator torquerequest. The associated engine input comprises at least one of apreferred engine input speed (‘Ni*’), a preferred engine input power(‘Pi*’), and a preferred engine input torque (‘Ti*’) that is responsiveto and preferably meets the operator torque request. The operating rangestate analyzer 260 evaluates M1-Engine Off (264) and M2-Engine Off (266)to determine a preferred cost (‘P*cost’) for operating the powertrainsystem responsive to and preferably meeting the operator torque requestwhen the engine 14 is in the engine-off state.

The preferred operation in each of G1 (270), G2 (272), G3 (274), and G4(276) can be determined by executing a 1-dimensional search scheme 610.

FIG. 8 schematically shows signal flow for the 1-dimension search scheme610. The operator torque request (‘Operator Torque Request’), and arange of one controllable input, in this embodiment comprising minimumand maximum input torques (‘TiMin/Max’), are input to a 1-D searchengine 415. The 1-D search engine 415 iteratively generates candidateinput torques (‘Ti(j)’) which range between the minimum and maximuminput torques, each which is input to an optimization function (‘OptTo/Ta/Tb’) 440, for n search iterations. Other inputs to theoptimization function 440 include system inputs preferably compriseparametric states for battery power, clutch torques, electric motoroperation, transmission and engine operation, and the specific operatingrange state. The optimization function 440 determines transmissionoperation comprising an output torque, motor torques, and associatedbattery and electrical powers (‘To(j), Ta(j), Tb(j), Pbat(j), Pa(j),Pb(j)’) associated with the candidate input torque based upon the systeminputs in response to the operator torque request for the candidateoperating range state. The output torque, motor torques, and associatedbattery powers, penalty costs, and power cost inputs are input to a costfunction 450, which executes to determine a power cost (‘Pcost(j)’) foroperating the powertrain in the candidate operating range state at thecandidate input torque in response to the operator torque request. The1-D search engine 415 iteratively generates candidate input torques overthe range of input torques. The candidate input torques are inputted tothe optimization function 440 and the cost function 450 to determine thepower costs associated therewith to identify a preferred input torque(‘Ti*’) and associated preferred cost (‘P*cost’). The preferred inputtorque (‘Ti*’) comprises the candidate input torque within the range ofinput torques that results in a minimum power cost of the candidateoperating range state, i.e., the preferred cost.

The preferred operation in each of M1 (262) and M2 (264) can bedetermined by executing a 2-dimensional search scheme 620. FIG. 9schematically shows signal flow for the 2-dimension search scheme 620.Ranges of two controllable inputs, in this embodiment comprising minimumand maximum input speeds (‘Ni Min/Max’) and minimum and maximum inputpowers (‘Pi Min/Max’), are input to a 2-D search engine 410. In anotherembodiment, the two controllable inputs can comprise minimum and maximuminput speeds and minimum and maximum input torques. The 2-D searchengine 410 iteratively generates candidate input speeds (‘Ni(j)’) andcandidate input powers (‘Pi(j)’) which range between the minimum andmaximum input speeds and powers. The candidate input power is preferablyconverted to a candidate input torque (‘Ti(j)’) (412). Each candidateinput speed (‘Ni(j)’) and candidate input torque (‘Ti(j)’) are input toan optimization function (‘Opt To/Ta/Tb’) 440, for n search iterations.Other inputs to the optimization function 440 include system inputspreferably comprising parametric states for battery power, clutchtorques, electric motor operation, transmission and engine operation,the specific operating range state and the operator torque request. Theoptimization function 440 determines transmission operation comprisingan output torque, motor torques, and associated battery and electricalpowers (‘To(j), Ta(j), Tb(j), Pbat(j), Pa(j), Pb(j)’) associated withthe candidate input power and candidate input speed based upon thesystem inputs and the operating torque request for the candidateoperating range state. The output torque, motor torques, and associatedbattery powers, penalty costs and power cost inputs are input to a costfunction 450, which executes to determine a power cost (‘Pcost(j)’) foroperating the powertrain at the candidate input power and candidateinput speed in response to the operator torque request in the candidateoperating range state. The 2-D search engine 410 iteratively generatesthe candidate input speeds and candidate input powers over the range ofinput speeds and range of input powers and determines the power costsassociated therewith to identify a preferred input power (‘Pi*’) andpreferred input speed (‘Ni*’) and associated preferred cost (‘P*cost’).The preferred input power (‘Pi*’) and preferred input speed (‘Ni*’)comprises the candidate input power and candidate input speed thatresult in a minimum power cost for the candidate operating range state.

FIG. 10 schematically shows power flow and power losses through hybridpowertrain system, in context of the exemplary powertrain systemdescribed above. There is a first power flow path from a fuel storagesystem 9 which transfers fuel power (‘P_(FUEL)’) to the engine 14 whichtransfers input power (‘P_(I)’) to the transmission 10. The power lossin the first flow path comprises engine power losses (‘P_(LOSS ENG)’).There is a second power flow path which transfers electric power(‘P_(BAT)’) from the ESD 74 to the TPIM 19 which transfers electricpower (‘P_(INV ELEC)’) to the first and second electric machines 56 and72 which transfer motor mechanical power (‘P_(MOTOR MECH)’) to thetransmission 10. The power losses in the second power flow path includebattery power losses (‘P_(LOSS BATT)’) and electric motor power losses(‘P_(LOSS MOTOR)’). The TPIM 19 has an electric power load(‘P_(HV LOAD)’) that services electric loads in the system (‘HV Loads’),which can include a low voltage battery storage system (not shown). Thetransmission 10 has a mechanical inertia power input (‘P_(INERTIA)’) inthe system (‘Inertia Storage’) that preferably include inertias from theengine 14 and the transmission 10. The transmission 10 has mechanicalpower losses (‘P_(LOSS MECH)’) and power output (‘P_(OUT)’). The brakesystem 94 has brake power losses (‘P_(LOSS BRAKE)’) and the remainingpower is transferred to the driveline as axle power (‘P_(AXLE)’).

The power cost inputs to the cost function 450 are determined based uponfactors related to vehicle driveability, fuel economy, emissions, andbattery usage. Power costs are assigned and associated with fuel andelectrical power consumption and are associated with a specificoperating points of the hybrid powertrain. Lower operating costs can beassociated with lower fuel consumption at high conversion efficiencies,lower battery power usage, and lower emissions for each enginespeed/load operating point, and take into account the candidateoperating state of the engine 14. As described hereinabove, the powercosts may include the engine power losses (‘P_(LOSS ENG)’), electricmotor power losses (‘P_(LOSS MOTOR)’), battery power losses(‘P_(LOSS BATT)’), brake power losses (‘P_(LOSS BRAKE)’), and mechanicalpower losses (‘P_(LOSS MECH)’) associated with operating the hybridpowertrain at a specific operating point which includes input speed,motor speeds, input torque, motor torques, a transmission operatingrange state and an engine state.

The state stabilization and arbitration block 280 selects a preferredtransmission operating range state (‘Hybrid Range State Des’) whichpreferably is the transmission operating range state associated with theminimum preferred cost for the allowed operating range states outputfrom the operating range state analyzer 260, taking into account factorsrelated to arbitrating effects of changing the operating range state onthe operation of the transmission to effect stable powertrain operation.The preferred input speed (‘Ni_Des’) is the engine input speedassociated with the preferred engine input comprising the preferredengine input speed (‘Ni*’), the preferred engine input power (‘Pi*’),and the preferred engine input torque (‘Ti*’) that is responsive to andpreferably meets the operator torque request for the selected preferredoperating range state.

FIG. 11 schematically shows the cost function 450 used by the strategicoptimization control scheme 310 and the tactical control scheme 330 todetermine a power loss cost P_(COST)(j) for iteratively selectedcandidate powertrain system operating points. The cost function 450determines operating costs in units of power (for example, kilowatts ofpower) for each candidate powertrain system operating point. The costfunction 450 includes an input torque cost function 508 (‘Input TorqueCost’), a clutch torque cost function 510 (‘Clutch Torque Cost’), an ESDcost function 512 (‘Energy Storage Device Cost’), an electric machinecost function 514 (‘Electric Machine Motor Torque Cost’), and a costsummation function 518.

The input torque cost function 508 determines an engine input torquepower cost P_(COST) _(—) _(TI)(j) for operating the engine to achievethe candidate input torque T_(I)(j). The clutch torque cost function 510determines a clutch torque power cost P_(COST) _(—) _(CL)(j) associatedwith the transmission clutch torque T_(CL)(j) corresponding to thecandidate powertrain operating point (j). The ESD cost function 512determines an ESD power cost P_(COST) _(—) _(BAT)(j) associated with theESD output power P_(BAT)(j) corresponding to the candidate powertrainoperating point (j). The electric machine cost function 514 determinesan electric machine cost P_(COST) _(—) _(EM)(j) associated withoperating the electric machine(s) corresponding to the candidatepowertrain operating point (j). Inputs include the first electricmachine motor torque T_(A)(j), the second electric machine motor torqueT_(B)(j), the ESD 74 output power to the first electric machine P_(ELEC)_(—) _(A)(j), and the ESD 74 output power to the second electric machineP_(ELEC) _(—) _(B)(j), each of which corresponds to the candidatepowertrain operating point (j). Other inputs include the first electricmachine motor speed N_(A) and the second electric machine motor speedN_(B), a first electric machine temperature cost multiplier (‘TempA CostMultiplier’), and a second electric machine temperature cost multiplier(‘TempB Cost Multiplier’).

FIG. 12 schematically shows details of the electric machine costfunction 514, including a first mechanical power determination 556(‘Mechanical Power Determination A’), a second mechanical powerdetermination 558 (‘Mechanical Power Determination B’), a first powerloss function 560 (‘Electric Machine Power Loss Function A’), a secondpower loss function 562 (‘Electric Machine Power Loss Function B’), afirst cost function 564 (‘Power Loss Cost Function A’), a second costfunction 566 (‘Power Loss Cost Function B’) and a summation function 568(‘Summation’).

Temperatures of the first and second electric machines 56 and 72 aremonitored (‘TempA’, ‘TempB’) and input to corresponding predeterminedcalibrations 552 and 554 (‘TempA Cost. Mult. Determination’ and ‘TempBCost. Mult. Determination’) to determine the first electric machinetemperature cost multiplier (‘TempA Cost Mult.’) and the second electricmachine temperature cost multiplier (‘TempB Cost Mult.’). The firstelectric machine temperature is input into the first cost multiplierdetermination 552 and the second electric machine temperature is inputinto the second cost multiplier determination 554. The first electricmachine temperature and the second electric machine temperature cancomprise temperatures monitored at any of a plurality of locationswithin the first and second electric machines 56 and 72, respectively.Exemplary locations include the stator, the rotor, resolvers 80, 82, andthe TPIM 19 including within various electronic components within theTPIM 19, e.g., electronic components proximate to integrated gatebipolar transistors (IGBTs) (not shown.) Further, temperature can bemonitored in multiple locations and the electric machine cost function514 can utilize multiple temperature inputs when determining operatingelectric machine cost P_(COST) _(—) _(EM)(j).

The first and second cost multiplier determinations 552 and 554 eachaccess a lookup table to determine a first cost multiplier (‘TempA CostMult.’) and a second cost multiplier (‘TempB Cost Mult.’), respectively,based upon the first electric machine temperature and the secondelectric machine temperature, respectively. The first and second costmultipliers generally increase with increasing temperature. In oneembodiment, the cost multipliers increase with increasing temperaturefor temperatures below a first threshold temperature, and are relativelyconstant for temperatures between the first threshold temperature and asecond threshold temperature, and generally increase with increasingtemperature above the second threshold temperature. The cost multipliersreflect electric power costs associated with operating an electricmachine associated with operating temperature. The cost multipliers areexecuted to bias operation away from powertrain system operating pointsthat generate increased amounts of heat within the first and secondelectric machines 56 and 72 operating at high temperatures.

The first mechanical power determination 556 determines an actual motorpower output Pa(j) from the first electric machine 56 by multiplying themotor speed N_(A) by the motor torque T_(A)(j). The second mechanicalpower determination 558 determines an actual motor power output Pb(j)from the second electric machine 72 by multiplying motor speed N_(B) bythe motor torque T_(B)(j).

The power loss function 560 determines a power loss (‘Power Loss A’)within the first electric machine 56 by subtracting the ESD power inputto the first electric machine (‘P_(A)(j)’) from the actual motor poweroutput Pa(j) from the first electric machine 56. The power loss function566 determines a second power loss (‘Power Loss B’) within the secondelectric machine 72 by subtracting the ESD power output to the secondelectric machine (‘P_(B)(j)’) from actual motor power output Pb(j) fromthe second electric machine 72.

The first cost function 564 determines a first electric machineoperating cost (‘Cost A’) by multiplying the first power loss (‘PowerLoss A’) by the first cost multiplier (‘TempA Cost Mult.’). The costfunction 566 determines a second electric machine operating cost (‘CostB’) by multiplying the second power loss (‘Power Loss B’) by the secondcost multiplier (‘TempB Cost Mult.’). The summation function 568determines the total electric machine cost (‘P_(COST) _(—) _(EM)(j)’)for the operating point by summing the first electric machine cost andthe second electric machine cost.

Referring again to FIG. 11, the cost summation function 518 (‘CostSummation’) determines the cost for each powertrain system point(‘P_(COST)(j)’) by summing the transmission clutch torque cost, theengine input torque cost, the electric machine cost, and the ESD powercost.

The cost function 450 determines power costs power associated withoperating the engine 14 and the first and second electric machines 56and 72 to in response to the output torque request for candidate enginestates and candidate transmission operating range states. The first andsecond cost multiplier allows the cost function 450 to consider firstand second electric machine temperatures in addition to power losseswhen determining the preferred powertrain system operating point. Thefirst and second cost multiplier can multiply first and second electricmachine temperatures by a small number, for example a number less thanone, when the first and second electric machine temperatures are lessthan the preferred temperature range to determine electric machinecosts, thereby decreasing the electric machine cost. When motor poweroutputs P_(A) and P_(B) increase the first and second electric machinetemperatures generally increase, thereby controlling the first andsecond electric machine temperatures to the preferred temperature range.The first and second cost multiplier can multiply first and secondelectric machine temperatures by a large number, for example a numbergreater than one, when the first and second electric machinetemperatures is greater than the preferred temperature range todetermine electric machine costs, thereby decreasing the electricmachine cost. When motor power outputs P_(A) and P_(B) decrease thefirst and second electric machine temperatures generally decrease,thereby controlling the first and second electric machine temperaturesto the preferred temperature range.

The disclosure has described certain preferred embodiments andmodifications thereto. Further modifications and alterations may occurto others upon reading and understanding the specification. Therefore,it is intended that the disclosure not be limited to the particularembodiment(s) disclosed as the best mode contemplated for carrying outthis disclosure, but that the disclosure will include all embodimentsfalling within the scope of the appended claims.

1. Method for controlling a powertrain system comprising an enginecoupled to an input member of a transmission device operative totransmit torque between the input member and a torque machine and anoutput member, the torque machine connected to an energy storage device,the method comprising: monitoring a temperature of the torque machine;selecting a candidate powertrain system operating point; determining anelectrical power input and a motor power output of the torque machinefor the candidate powertrain system operating point; determining a powerloss for the torque machine associated with the motor power output ofthe torque machine and the electrical power input; executing atemperature cost modifier value of the torque machine accessed from alook-up table based on the monitored temperature of the torque machineto bias operation away from powertrain system operating points thatgenerate increased temperature within the torque machine; anddetermining operating costs for operating the powertrain system at thecandidate powertrain system operating point associated with the powerloss from the torque machine and based upon the temperature costmodifier value of the torque machine.
 2. The method of claim 1, whereinmonitoring a temperature of the torque machine comprises monitoring atemperature of a motor of the torque machine.
 3. The method of claim 1,wherein monitoring a temperature of the torque machine comprisesmonitoring a temperature of an inverter of a torque machine.
 4. Themethod of claim 1, further comprising: determining an operating costbased upon the torque machine by multiplying the temperature costmodifier value by the power loss value of the torque machine.
 5. Themethod of claim 4, further comprising: determining a preferredtemperature range for the torque machine; and determining thetemperature cost modifier value based on a proximity of the temperatureof the torque machine to the preferred temperature range.
 6. The methodof claim 1, further comprising: monitoring multiple temperatures of thetorque machine; and determining operating costs for operating thepowertrain system at the candidate powertrain system operating pointassociated with the power loss from the torque machine and based uponmultiple temperatures of the torque machine.
 7. Method for controlling apowertrain system comprising an engine coupled to an input member of atransmission device operative to transmit torque between the inputmember and a torque machine and an output member, the torque machineconnected to an energy storage device, the method comprising: monitoringa temperature of the torque machine; selecting a candidate powertrainsystem operating point; determining an electrical power input and amotor power output of the torque machine for the candidate powertrainsystem operating point; determining a power loss for the torque machineassociated with the motor power output of the torque machine and theelectrical power input; determining operating costs for operating thepowertrain system at the candidate powertrain system operating pointassociated with the power loss from the torque machine and based uponthe temperature of the torque machine; iteratively selecting candidatepowertrain system operating points; determining operating costs foroperating the powertrain system at each candidate powertrain systemoperating point associated with the power loss from the torque machineand based upon the temperature of the torque machine; and selecting apreferred powertrain system operating point comprising the candidatepowertrain system operating point having a minimum operating cost foroperating the powertrain system.
 8. The method of claim 7, furthercomprising: iteratively selecting candidate engine operating points;determining operating costs for operating the powertrain system at eachcandidate engine operating point associated with the power loss from thetorque machine and based upon the temperature of the torque machine; andselecting a preferred engine operating point comprising the candidateengine operating point having a minimum operating cost for operating thepowertrain system.
 9. The method of claim 8, further comprising:iteratively selecting candidate engine operating points includingcandidate engine states and candidate engine input power; determiningoperating costs for operating the powertrain system at each candidateengine state and candidate engine input power associated with the powerloss from the torque machine and based upon the temperature of thetorque machine; and selecting a preferred engine state and engine inputpower comprising the candidate engine state and candidate engine inputpower having a minimum operating cost for operating the powertrainsystem.
 10. The method of claim 9, wherein the candidate engine stateincludes a fueled, all-cylinder engine state, a fuel-cutoff deactivationengine state, an fuel-cutoff all-cylinder engine state, and afuel-cutoff cylinder deactivation engine state.
 11. The method of claim7, further comprising iteratively selecting transmission operating rangestates; determining operating costs for operating the powertrain systemat each candidate transmission operating range state based associatedwith power loss from the torque machine and based upon the temperatureof the torque machine; and selecting a preferred transmission operatingrange state comprising the candidate transmission operating range statehaving a minimum operating cost for operating the powertrain system. 12.The method of claim 11, wherein the candidate transmission operatingrange state includes a fixed gear operating range state and acontinuously variable operating range state.
 13. Method for controllinga powertrain system comprising an engine coupled to an input member of atransmission device operative to transmit torque between the inputmember and first and second torque machines and an output member, thetorque machines connected to an energy storage device, the methodcomprising: monitoring a temperature of the first electric machine;monitoring a temperature of the second electric machine; selecting acandidate powertrain system operating point; determining a electricpower output and a motor power output of the first electric machine forthe candidate powertrain system operating point; determining a electricpower output and a motor power output of the second electric machine forthe candidate powertrain system operating point; determining a powerloss value of the first electric machine based upon the first motorpower output and the first electric power output; determining a powerloss value of the second electric machine based upon the second motorpower output and the second electric power output; and determining anoperating cost for operating the powertrain system associated with thepower loss value from the first electric machine, the power loss valuefrom the second electric machine, the temperature of the first electricmachine, and the temperature of the second electric machine.
 14. Themethod of claim 13, wherein monitoring a temperature of the firstelectric machine comprises monitoring a temperature of a motor of thefirst electric machine.
 15. The method of claim 13, wherein monitoring atemperature of the first electric machine comprises monitoring atemperature of an inverter of the first electric machine.
 16. The methodof claim 13, further comprising: determining a preferred temperaturerange for the first electric machine; and determining the cost modifiervalue based on a proximity of the temperature of the first electricmachine to the preferred temperature range.
 17. The method of claim 16,wherein the candidate powertrain system operating point comprises atleast one of a candidate engine operating point and a candidatetransmission operating range state.
 18. The method of claim 17, whereinthe candidate engine operating point comprises at least one of acandidate engine state, a candidate engine speed, a candidate enginetorque, and a candidate engine power.
 19. Method for controlling apowertrain system comprising an engine coupled to an input member of atransmission device operative to transmit torque between the inputmember and first and second electric machines and an output member, thefirst and second electric machines connected to an energy storagedevice, the method comprising: monitoring temperatures of the first andsecond electric machines; iteratively selecting candidate powertrainoperating points; determining an electrical power input and a motorpower output of the first and second electric machines for eachcandidate powertrain system operating point; determining a power lossfor the first and second electric machines associated with the motorpower output and the electrical power input and the temperatures of thefirst and second electric machines; determining operating costs foroperating the powertrain system at the candidate powertrain systemoperating point associated with the power loss for the first and secondelectric machines; selecting a preferred powertrain operating pointcomprising the candidate powertrain operating point having a minimumoperating cost for operating the powertrain system; and controllingoperation of the powertrain system based upon the preferred powertrainoperating point.
 20. The method of claim 19, wherein the candidatepowertrain operating point comprises a candidate engine state, acandidate engine power, and a candidate transmission operating rangestate.